Photochemical: Sun dried leaves contain two resins, one that is insoluble in alcohol forming the larger portion and other soluble in alcohol. The resin soluble in alcohol has tingling sensation in throat. It contains no tannins. It also contains new bitter neutral principle, albuminous and coloring matters, calcium oxalate, pararabin, glucose, carbohydrates, some tartaric acid and an organic acid alike glucoside that has anti-saccharine properties. The Plant also contains gymnemic acids, saponins, stigmasterol, quercitol, and the amino acid derivatives betaine, choline and trimethylamine

Respiratory system: powdered leaves are given in rhinitis, asthma and bronchial cough Nutrition and metabolism: it controls diabetes.

Action of Gymnema SylvestreThe action of enzymes isolated from G. Sylvestre was studied in vitro on both cane sugar and glucose and the following results were obtained

The reducing substance presenting the leaves was found to be 0.37 %Hydrolytic action was seen within two hours when powdered leaves were mixed in cane sugar solution. The action was completed in 18 hours. The same result was seen when cane sugar was mixed with enzyme isolated from the leaves. The powdered leaves were found to have an oxidose action on glucose solution and glycolysis occurred which reduced the strength of glucose solution from 2.3 to 0.66 % in 29 hours. In the enzymes isolated from the leaves no such action was seen.The gymnemic acid was found to have neither hydrolytic nor oxidose action when mixed with cane sugar or glucose.

According to Mhaskar and Caius the leaves cause hypoglycemia in experimental animals, which sets in soon after the administration either by mouth or by injection. This hypoglycemia has been explained on the assumption that the drug acts indirectly through stimulation in insulin secretion of the pancreas, as it has no direct action on he carbohydrate metabolism.

Recent pharmacological and clinical studies have shown that Gymnema Sylvestre acts on two sites:

First, the taste buds in the oral cavity;

Second, the absorptive surface to the intestines.

The structure of those taste buds, which detect sugar in the mouth, is similar to the structure of the tissue that absorbs sugar in the intestine. The important active ingredient of Gymnema Sylvestre is an organic acid called "gymnemic acid." The gymnemic acid is made up of molecules that see the arrangement is similar to that of glucose molecules. Those molecules fill the receptor locations on the taste buds for a period of one to two hours, thereby preventing the taste buds from being activated by any sugar molecules present in the food. Similarly, the glucose-like molecules in the gymnemic acid fill the receptor locations in the absorptive external layers of the intestine, thereby preventing the intestine from absorbing the sugar molecules.
It has also been noted that Gymnema Sylvestre takes away the bitter taste of bitter substances, such as quinine, in much the same way that it affects the sense of sweetness associated with candies and other sweet foods. However, it has no effect on pungent, salty, astringent or acidic tastes. Therefore, if you were eating an orange within two hours after chewing Gymnema Sylvestre leaves; for instance, you would taste the sourness of it but not the sweetness.

Role of gurmar in controlling hyperglycemia:

Extracts of G. Sylvestre given to patients with type I diabetes on insulin therapy reduces insulin requirements and fasting blood sugar levels, and improves blood sugar control. In a study of type II diabetics, Gymnema extract given along with oral hypoglycemic drugs was shown to improve blood sugar control and to either lead to discontinuation of the medicine or a significantly reduced dosage. It is interesting to note that Gymnema extract given to healthy volunteers does not produce any blood sugar-lowering, or hypoglycemic, effectsIn a controlled study, a standardized Gymnema extract was given to 27 type 1 diabetics at a dose of 400 mg daily for 6-30 months. Thirty-seven others continued on insulin therapy alone and were tracked for 10-12 months. Insulin requirements were decreased by about one-half and the average blood glucose decreased from 232 mg/dL to 152 mg/dL in the Gymnema group. The control group showed no significant decreases in blood sugar or insulin requirement. In addition, there was a statistically significant decrease in glycosylated hemoglobin (HbA1c) after 6-8 months on Gymnema when compared to either the pretreatment levels or the control group. Twenty-two type 2 diabetics were administered 400 mg Gymnema extract daily for 18-20 months in addition to their oral hypoglycemic medications. This group experienced significant decreases in average blood sugar and HbA1c, and an increase in pancreatic release of insulin. Medication dosages were decreased, and five were able to discontinue drugs entirely.

Two water-soluble extracts, GS3 and GS4, obtained
from the leaves of Gymnema Sylvestre, were tested
in streptozotocin treated rats for their effects
on blood glucose homeostasis and pancreatic
endocrine tissue. In the diabetic rats, fasting
blood glucose levels returned to normal after
60 days of GS3 and after 20 days of GS4 oral
administration. Blood collected during the conduct
of oral glucose tolerance tests was used to
assay for serum insulin. GS3 and GS4 therapy
led to a rise in serum insulin to levels closer
to normal fasting levels. In diabetic rat pancreas,
both GS3 and GS4 were able to double the islet
number and beta cell number. This herbal therapy
appears to bring about blood glucose homeostasis
through increased serum insulin levels provided
by repair/regeneration of the endocrine pancreas.Enzyme
changes and glucose utilization in diabetic
rabbits: the effect of Gymnema Sylvestre, R.BrShanmugasundaram
KR, Panneerselvam C, Samudram P, Shanmugasundaram
ER.The administration of the dried leaf powder
of Gymnema Sylvestre regulates the blood sugar
levels in alloxan diabetic rabbits. G. Sylvestre
therapy not only produced blood glucose homeostasis
but also increased the activities of the enzymes
affording the utilization of glucose by insulin
dependent pathways: it controlled phosphorylase
levels, gluconeogenic enzymes and sorbitol dehydrogenase.
The uptake and incorporation of [14C] glucose
into the glycogen and protein are increased
in the liver, kidney and muscle in G. Sylvestre
administered diabetic animals when compared
to the untreated diabetic animals. Controlling
hyperglycemia by G. sylvestre reverses pathological
changes initiated in the liver during the hyperglycemic
phase. G. Sylvestre, a herb used for the control
of diabetes mellitus in several parts of India,
appears to correct the metabolic derangements
in diabetic rabbit liver, kidney and muscle.

Anti diabetic effect exerted by leaf extract from Gymnema Sylvestre in NIDDM patients.Baskaran K, Kizar Ahamath B, Radha Shanmugasundaram K, Shanmugasundaram ER.Department of Biochemistry, Postgraduate Institute of Basic Medical Sciences, Madras, IndiaThe effectiveness of GS4, an extract from the leaves of Gymnema Sylvestre, in controlling hyperglycemia was investigated in 22 Type 2 diabetic patients on conventional oral anti-hyperglycemic agents. GS4 (400 mg/day) was administered for 18-20 months as a supplement to the conventional oral drugs. During GS4 supplementation, the patients showed a significant reduction in blood glucose, glycosylated hemoglobin and glycosylated plasma proteins, and conventional drug dosage could be decreased. Five of the 22 diabetic patients were able to discontinue their conventional drug and maintain their blood glucose homeostasis with GS4 alone. These data suggest that the beta cells may be regenerated/repaired in Type 2 diabetic patients on GS4 supplementation. This is supported by the appearance of raised insulin levels in the serum of patients after GS4 supplementation.